Metal rolling



F. B. CROSBY METAL ROLLING Feb. 1, 1944. 2,340,646

2 Sheets-Sheet 1 Filed Oct. 31, 1941 f2- 3 NVENTOR FRED B.CROSBY AT7ORNEY Feb. l, 1944. F. B.-CROSBY METAL ROLLING 2 She.ets-Sheet 2 Filed Oct. 51, 1941 oursoa DIA METER o=- com CHES) /j: 6

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Iatcnted Feb. 15 1944 -ZUITED STATES; PATENT, OFFICE Fred B. Crosby, Woicester, Masa, assignor to Mor- .gan Construction Company, Worcester, Mass.,,

a corporation of Massachusetts. Application October 31, 1941, Serial No.

. V 6 Claims. This invention 'relates to metal rolling, and

' more particularly to.:-apparatus for rollin'g and coiling flat metal strips.

In the production of long flat strips of metal itis a common practice to-wind the stock into spiral coils as it issues from the rolling 'mll. It has been found that the process is facilitated and an improved product obtained by maintaining a considerable tension in the Stock between the mill rolls and the,drum or reel on which the coli is formed. To prevent variations nthe thickness a'nd 'othencharacteristcs of the stock it is important that the tension remain substantially uniform throughout the formation of, the entire coll. This has been recoghiz ed, and certain electrical apparatus has been developed which will operate with a high degree of satisfaction to maintain the tension at a desired value. However such apparats is so cmplicated and expensive as to render its use economically uhjustified except in connection With large mills "in which-very high production rates are maintained. Consequently it has become customtry, in connection with the smaller mills,'to employ a relatively 'inexpensive continuously slipping friction drive for the reels, for example a belt and pulley drive or a friction clutch. Since such mechanisms are required to slip continuously during the build up'of the coll, they waste large amounts of power and they wear out very rapidly. Furthermore, they transmit a substantially constant torque to the reel, and since the diameterof the coll increases continuously during its formation the resultwill be continuous and very serious reduction in the stock tension. For example, assume that in a particular installation strip is to be rolied and formed into coils with an inside diameter of 16 inches and an outside diameter of 30 inches, the reel being driven by a slipping friction clutch which transmits a torque of 1600 inch-pounds. At the start of the coll the tension in the strip will be 200 pounds, but by the time the 30 inch diameter is reached this 'terision will have dropped to approximately 107 munds. With such an apparatus it will be impossible to produce a strip of uniform characteristics through its length.

It is acc0rdingiy the main object of the invention to provide a comparatively simple and inox-- pensive apparatus for rolling and coiling strip metal stock with a substaritially uniform tension. It is a further obiect of the invention to provide an apparatus which Will roll and coll strip metal stock with a substantially iinform tension and which will be eflicient in operation and free from wear.

It is a further object of the Invention to provide a simple, inexpensive and dependable appa ratus adapted to roll alnd coil strip metal stock with a substantially uniform tension and so constructed that the .tension may be readily adjusted in a simple manner. Y

With these andother objects in view. as will be apparent to those skilled in the art, the in vehtion resides in the combination of parts set forth .in the specifiction and covered by the claims appended hereto.

Refrring' to the drawings illustrating one emon the line 2-2 of strip stock;

Fig. 5 is a chart showing the -mannerin which the torque exerted by the clutch varies with its slip; and- Fig. 6 is a chart showing the manner in which the tension exerted on the stock varies during the formation of a coil.

The embodiment illustrated includes a roll stand (Fig. 1) for the production of flat strip) metal and comprising a pair of cylindrical work rolls lll (one only being shown). This roll stand may be of the our-hightype.' Each work roll ll) is connected by a spindle El to a pinion |2 in-known manner. The pinions are driven by (ii) -means of an electric motor M connectedthereto by a pinion l5 and a gea'r IG. At the delivery side of the rolls IE there is mounted a rotatable drum or reel I8 on which the stock may be wound as it issues from the rolls, to form a spiral coil. In order to drive this reel I provide an eddy current clutch I9 having an input shaft 20 connected to the gear lt and an output shaft 22 j bodiment oi the invention and in which like ref which ratus), varies during the formation of a coll of As illusttated, this clutch remain uniform, a pilot ball bearing -33 is pro vided between the central portions of the members 29 and 30. The output member is provided with a, coil '34 which is connected by conductors (not shown) to a, pair of slip rings carried by the shaft 22 and of course insulated therefrom. These rings are enga'ged by brushes 3C so that electric,current may be supplied to the coil to energize the same.

As shown in Fig. 3, the coil 34 is energized from a suitable source 38 of direct current, there be- 8 an ammeter 39 and a rheostat in series with the coil.

to be connected in parallel with the rheostat 40 by merely closing a, normally open switch 43, which is shown as of the push button type. The ammeter 39 will indicate exciting current through the coil.

Energization of the coil 34 creates a magnetic field, and the lines of magnetic flux pass through the peripheral portions of the two members 29 and IO. .If the input member 28 is rotating ata higher speed than the output member 30, the metal parts will cut across these lines of flux,

and electrical eddy currents win be induced. The direction of flow of these eddy currents will be,

such, with respect to the magnetic field, that they will create a magnetc drag which will tend to A second rheostat 42 is ranged the rate'oifiow of the check the relative motion between the input-and output members, thereby transmittng torque to the output member tending to rotate this member in the same rotating. Not only does this torque increase with an increasein the exciting current, but it also increases with an increase in the clutch slip, i. e.,

' the difierenc between the speeds of the input and output members. This relationship is shown in Fig. 5 for one particular size and construction of eddy current clutch, the figures at the righthand ends ot the several curves indicating the c0rresponding exciting currents in amperes.

It will also beapparent that during the formation oi a coil, the outside -diameter of the coil will increase at a steady rate, while the peripheral speed of the coil will remain equal to the speed oidelivery of the stock by the rolls II. Consequent ly, the rate of rotation of the drum l8 relative to that of the rolls Hi must decrease while a coil is being formed, and this necessarily involvesa corresponding increase in the slip of the clutch IS. This relationship is shown in Fig. 4, and it may be ascertained by calculation for any particular installation. For example, let us assume that the rolls IO are 4325 inches in diameter, the drum i8 is 1'6 inches in diameter, and the ratio of the pulleys 25-23 is 2.94 to 1. If now the rolls ll! are driven at 180 revolutions per minute, the delivery speed of the stock will be approximately '.l he speed of{the drum l8 coilwill be =200 feet per minute the of the clutchoutputmember will be 2,94X47.7=I2 R. P. M.,-and the clutch SIIJ Will b -140.2=39,8 R. P. M. Similarly'. by the at the start of eachdirection as the input member is 40 its maximuni dia'meter. For example}- the chartof .55 ampere,

the speed oi' the drum will'havedecreased to the speed of the clutch output member will be 2.94 X.25.47=74.9 R. P. M., and the clutch slip will be 18074.9=1Q5.1 R. P.M. The clutch slip for intermediate diameters of the coil is indicated by o the straight line shown in Fig. 4' and joining the two points determined by calculation. In the operation of the invention the slip of the clutch l9 wil1 increase during the growth of the coil, as explained above, and for a given excitation of the clutch the torque transmittedthereby will increase as shown in'Fig. S. Consequently the torque transmitted to the drum l8 will increase continuously as, the coil increasesin diameter, thereby counteracting the tendency for the o tension in the stock to deerease because of the increased moment arm through which it resists the drum rotation. As a result it is possible to maintain a substantially constant tension in the stock by-merely setting the rheostat 40 to produce the 5 desiredexeitation current, as indicated by the amineter 39, and leaving this adjustment unchanged during the formation of the coil. In Fig. 6 the actual stock tensions which will be maintained with various excitation currents and one particular clutch are shown by the curves, the figures at the right-hand ends of the curves indicating the excitation current in amperes. 'Ihus, if the operator wishes to maintain a stock tension of 1'00 pounds, he will adjust the rheostat 40 to give an ammeter reading of .28, and as shown by the curve the tension will be held with considerable accuracy. With the higher values of exciting current there is a tendency for the tension to decrease appreciably as the coil approaches indicates that an exciting current 'of.55 ainpere will produce a tension of about 400 'pounds during the formation of the flrst part oithe-coil, but

switch 43. With the switch 43 open the-rheostat an exciting current and with the switclr 43 closed 40 will be adjusted to 'produce the rheostat 42will be adjusted to increase this current to .58 ampere. The operator will close the switch 43 as each coil reaches adiameter of about 24 inches, and during the formation of the remaining portion of the coil the tension will be that indicated by the .58 excitation curve', which is a considerably closer approximaton to the desired 400 pound line.

From the above 0. that the invention disclosure it will be apparent provides an apparatus which will roll and coil strip metal under tension, and maintain this tension with suflicient accuracy tor the great majority of installations. Furthermore,

. the apparatus is comparatively simple and inex- 0pensive, and thoroughly' dependablein Service,

there,being no slipping fricti0n surfaces subject to rapid wear and deterioration. Having thus described my invention, what 1 claim as new and desire to secure by Letters Pat- 0 ent is:

1. Apparatus for rolling and coiling flat metal ,strips comprising a rolling mill, a reel.arranged to wind the stock delivered by the mill into spiral coils while maintaining a, tension on the stock.- 75 an eddy Y current clutch having an input member to wind the stock delivered by tro-magnetic coil, the

' mined speed relationship,

and an output member, common means to drive the rolling mill and the input member in a predetermined speed relationship, and driving connections from the output member,to the reel.

2. A pparatus for rolling and coiling flat metal strips comprising a rolling mill. a. reeel arranged the mill into spiral coils while maintaining a tension on the stock; an eddy current clutch having a rotatable input member, a. rotatable output member, and an elecclutch being constructed to tran smit a torque which increases with increased clutch slip without change in the excitation current through the coil; common means to drive the rolling mill and the input member in a predetermined speeed relationship, and driving connections from the output member to the reel, the various parts being so constructed and arranged that as the diameter of each coil of stock increases the clutch slip will increase, thereby increasing the torque applied to. the reel and maintaining a substantially uniform tension on the stock.

3. Apparatus for rolling and coiling flat metal strips comprising a rolling mill, a reel arranged to wind the stock delivered by the mill into spiral coils while maintaimng a tension on the erable clutch slip which will incre'ase continuof stock has been partially completed and thus increase still further the torque applied to the -reel 5. Appara'tus for rolling and coiling flat metal strips comprising a rolling. mill, a reel to wind the stock delivered by the mill into spiral stock, an eddy current clutch having a rotatable input member, a rotatable output member, and an electro-magnetc coil, the clutch being constructed to transmit a torque which increases with increased clutch slip without change in the excitation current through the coil, common means to drive the rolling mill and the input member in a. predetermined speed relationship, and driving connections from the output member to the reel of such a speed ratio that at the start of each coil, with the peripheral speed of the reel equal to the delivery speed of the stock, there will be a considerable clutch slip which 7 will, increase continuously during the formation of the coil, thereby increasing the torque applied to the reel and m taining a substantially uniform tension on the stock.

4. Apparatus for rolling and coiling flat metal strips comprising a rolling mill, a reel arranged to wind the stock delivered by the mill into spiral coils while maintaining a tensionn the stock, an eddy current clutch having a. rotatable input member, a rotatable output member, and an electro-magntic coil, the clutch constructed to transmit a torque which increases with inspeed relationship,

coils while maintaining a tension on the stock, an eddy current clutch having a rotatable input member, a rotatable output member, and an 'electro-magnetc coil, the clutch being constructed to transmit a torque which increases with increased clutch slip without change in the excitation current through the coil, a rheostat,iri series with the coil, a second rheostat in parallel With the first rheostat, a switch in series with the second rheostat, common means to drive the rollin mill and the input member in a predetermined and driving connections from the output member to the reel of such a speed ratio that at the start of each coil, with the peripheral speed of the reel equal to the delivery speed of the stock, there will bea considerable clutch slip which will increase continuously during the formation of the coil, thereby increasing the torque applied to the reel, the said switch providing a means whereby the operator may increase the excitation of the clutch coil by a predetermined amount after the coil of stock has been partially completed and thus increase still.

further the torque applied to the reel.

6. Apparatus for rolling and coiling flat metal strips comprising a rollmg mill, a reel arranged to wind the stock delivered bythe mill into spiral coils while maintaining a tension on the stock, the reel being located close to the mill, and the stock traveling directly from the mill to the reel, an eddy current clutch having a rotatable input member, a rotatable output member, and an electro-niagnetic coil, the clutch being constructed to transmit a torque which increases with increased clutch slip without change in the excitation current through the coil, common means to drive the rolling mill and the input member in a predetermined speed relationship, and drivcreased clutch slip without change in the excitaing connections from the output member to the reel of such a speed ratio that at the start of each coil, with the peripheral speed of the reel equal to the delivery speed of the stock, there will be a considerable clutch slip which will increase continuously during the formation of the coil, thereby increasing the; maintalning a substantially uniform tension on the stock.

Y FRED B. CROSBY.

. 3 livery speed of thestock, there will be a considarranged torque applied to the reel and 

